Normal erection activity involves the coordination of a complex series of physiological and psychological factors. Anything that affects any one of these systems can cause impotence. Psychogenic impotence can be caused by e.g. anxiety, depression, tension and stress.
Physical impotence occurs when diseases or injury affects the nerves, blood vessels or hormones that control erectile ability. The major causes of physical impotence in the United States are diabetes mellitus, vascular diseases, impotence following radical surgery, spinal cord injury and other traumas, other endocrine problems and multiple sclerosis. Other causes include prostate infections, drug abuse, alcoholism and side effects of prescription medicines. Even smoking can interfere with normal erections.
It is estimated that about 10 million men in the United States suffer from impotence. Above the age of 60 about one of three are no longer able to achieve a suitable erection.
There are several medical treatment alternatives currently available depending on the nature and cause of the impotence problem, such as therapy with Yohimbine, an Indian tree bark extract, thought to chemically stimulate the nerves in penis that control erections. Early reports indicate that normal erection is restored in 20-25 percent of the patients, but the effect is disputable. Side effects may include dizziness, nausea, nervousness and headaches.
For some men with low male hormone (testosterone) levels treatment with testosterone injections or pills may be beneficial. However, most patients do not have low testosterone levels and will not benefit from supplemental hormones. The side effects of testosterone treatment are several.
In recent years patients with erectile dysfunction of various origin have been treated by intracorporeal injection of various drugs. One such medicament is papaverin, which in small amounts dilates the arterial blood vessels and decreases the venous drainage (Virag R., Intracavernous injection of papaverin for erectile failure. Letter to the editor. Lancet 1982; 2:938). Brindley, G. S. describes in Brit. J. Psychiat. (1983), 143, 332-337 a new technique for investigating and treating erectile impotence by intracavernous self-injection of small doses of phenoxybenzamine or phentolamine. The doses as used for intracorporeal injection are about 2-10 mg of phenoxybenzamine and about 0.5-1.5 mg of phentolamine.
The side effects of self-injection of medication are the risk of infection, bruises, fibrosis and scarring with permanent changes inside the penis. There is also a risk of painful longstanding erection (Priapism).
It is further known that intravenous or intramuscular injection of phentolamine in moderate doses can cause an excessive fall in blood-pressure due to peripheral vasodilatation which puts the patient into a state of circulatory shock.
Experimentally it has been shown in some cases that cutaneous application of nitroglycerine paste to some extent can enhance the quality of erection.
Further, surgical implantation of penile prosthesis have been performed when simpler treatments are unsuccessful. However, all surgical penile prosthetic implants carry a high risk of infection. Other complications of surgery include temporary urinary retention, pain, bleeding, scarring, mechanical failure and extrusion of the implant.